the rinse agent isn't necessary, just helpful because it can aid in knocking loose the particle bound ions better than water alone,... speaking of which, what source is yours? I gather a pH and ppm/EC reading isn't available now either,... LOL!- soil growing isn't as simplistic as many presume it to be, with little need for such equipment,.. some get away with it too on occasion, but when shit starts going south, and there's no means to measure important parameters, it becomes a difficult craps shoot to guess at the right way to fix things! Very likely, with salt n build-up and those symptoms, it's too acidic in there,... Still, you can flush anyway, and sooner is better!... I suggest using a mix of tap and DI/RO water, but that depends on your water source... if you know you have pretty hard water, high mineral content, then using lower EC/ppm water can help with the flushing,.. typically, I tell people to measure the pH and ppm of the run-off initially and as the flush progresses to see how bad it is in there, and how well it's correcting,.... At least 3x the pot volume is used, done quickly, 20min, so as to not water board them and start suffocating the roots! In the final pour, include a mild dose of nutes and Ca-Mg, like 1/4 strength,....I know air pots can make this process a real beating, with side leakage, so go slow, even and steady with the pour,... there's several flush agents out there, but the two mentioned are well spoken of,...